The authenticity of banknotes is protected by a variety of security features which may include security paper, security inks and the inclusion of security threads and foils.
Handheld devices and desktop machines for determining the validity of an authentic banknote are available.
WO 2005/076742 describes an apparatus and method for discriminating between authentic and forged banknotes. A handheld optical device is provided which illuminates indicia printed with security ink and measures the spectral absorption thereof at a plurality of discrete wavelengths. The device then compares these results with results to be expected from the scanning of the same defined feature of an authentic banknote. A display or other means informs the user whether or not the discrepancy between results and pre-stored values is within naturally occurring variations.